Many different processes for the conversion of cellulose into alkali cellulose for subsequent xanthation and viscose production are known in the art. Generally, wood pulp is converted into alkali cellulose by treatment with caustic steeping processes. The resulting alkali cellulose is then xanthated to form a soluble cellulose xanthate, which, after being treated with a dilute aqueous caustic solution, results in an acceptably filterable viscose.
One of the early processes for conversion of cellulose into alkali cellulose consists of treating sheets of cellulose with a dilute solution of NaOH, pressing the excess NaOH solution out of the resulting alkali cellulose and shredding the alkali cellulose into particles, which, upon xanthation, would produce an acceptably filterable viscose. This process, however, requires an excess of NaOH solution to achieve a desirable concentration of caustic in the cellulose. The excess NaOH pressed out of the cellulose is contaminated with hemi cellulose and hence is difficult to recycle into the alkalyzing step of the process. Further, significant degradation of the cellulose occurs due to the length of contact time with the excess NaOH solution.
In order to reduce NaOH waste, another process of the prior art contacts a measured quantity of pulverized cellulose with a mist of sprayed aqueous NaOH solution. The heart of this process is the suspension of the cellulose particles in the atmosphere of the reaction vessel using gaseous countercurrents until the particles are wetted with the caustic spray. Consequently, due to the increase in weight, these particles fall out of the atmosphere of the reaction chamber and out of contact with the caustic spray.